1. Field of the Invention
This invention relates to personal mobility vehicles and more particularly to an improved drive wheel suspension system for a central drive personal mobility vehicle.
2. Prior Art Statement
Persons with partial and total walking disabilities have traditionally relied upon wheelchairs for locomotion. Wheelchairs generally have relatively widely spaced wheels for lateral stability and to comfortably accommodate the occupant. Persons in wheelchairs can move with relative ease in places such as hospitals which are usually provided with extra wide doors and halls and inclined ramps between vertically displaced levels. However, private homes and work places are generally not planned specifically to accommodate wheelchairs.
While wheelchairs are generally resistant to lateral tipping, wheelchairs are often designed for tipping backwards so that an attendant pushing a patient in a wheelchair can tip the front wheels up to negotiate such obstacles as steps, thresholds, and the like. While such a configuration is useful when the wheelchair is pushed by an attendant, the design presents some hazards when the occupant of the wheelchair attempts to move the wheelchair up a ramp.
In order to overcome some of the problems associated with wheelchairs, the medical equipment industry has developed small personal mobility vehicles as an alternative to the conventional wheelchair. In general, rear wheel drive personal mobility vehicles have a pair of powered rear wheels and a steerable front wheel. The track of the powered rear wheels is generally narrower than a conventional wheelchair, while the wheel base is generally longer than a conventional wheelchair. The personal mobility vehicles are usually designed for a tight turning radius in order to be more maneuverable than a conventional wheelchair. Accordingly, rear wheel drive personal mobility vehicles may be used in places which are not specifically designed for conventional wheelchair use.
Among the most maneuverable personal mobility vehicles are central drive personal mobility vehicles. A central drive personal mobility vehicle has a right and a left drive wheel and a left and a right trailing wheel. The right and left drive wheels are located substantially below a seat of the central drive personal mobility vehicle enabling the central drive personal mobility vehicle to essentially turn around within the overall length of the central drive personal mobility vehicle.
Although the central drive personal mobility vehicles are the most maneuverable personal mobility vehicles, the central drive personal mobility vehicle have certain disadvantages over the rear wheel drive personal mobility vehicles.
Firstly, most operators perceive the central drive personal mobility vehicle to be less stable than the rear wheel drive personal mobility vehicle. This perceived instability of the central drive personal mobility vehicle by infirm or elderly operators limited the acceptance of the central drive personal mobility vehicle by the purchasing public.
Secondly, when the central drive personal mobility vehicle is decelerated, the central drive personal mobility vehicle tends to pitch forward about the right and left drive wheels. In order to increase stability and to reduce the pitch forward upon deceleration, the central drive personal mobility vehicles is provided with a left and a right leading wheel. The addition of the left and right leading wheels reduces but does not eliminate the above problems.
Thirdly, the central drive personal mobility vehicle is unable to adjust for different weight distributions of the different operators of the central drive personal mobility vehicle. The central drive personal mobility vehicle designed to provide stability for an operator with one weight distribution may be unstable for an operator with another weight distribution.
Many in the prior art have attempted to solve the above problems with varying degrees of success. The following United States Patents are representative of attempts of the prior art to eliminate the aforementioned problems and to provide a central drive personal mobility vehicle which satisfies the needs of the art.
U.S. Pat. No. 3,952,822 to Udden et al. discloses an electrically powered wheel-chair for indoor and outdoor use comprising a pair of rear main wheels which are non-pivotably connected with the framework of the chair. At least one of the wheels is driven by an electric motor. A steering wheel is rotatably connected with the framework of the wheelchair and is positioned in front of the main wheels. The steering wheel is asymmetrically located on one side of a longitudinal axis through the middle of the chair. A support wheel is positioned on the other side of the longitudinal axis relative to the steering wheel at such a level above a flat and horizontal ground surface that it will not touch this surface when the steering wheel directed straight ahead. The diameter of the support wheel is less than that of the steering wheel and the distance from the fore-most point of the steering wheel to a transverse axis through the centers of the main wheels is greater than the corresponding distance for the support wheel. To provide good stability the electric batteries are located in a case thus designed that the common center of gravity of the batteries will be located on the same side of the longitudinal axis of the chair as the steering wheel. The frame-work is equipped with two auxiliary support wheels on either side of the chair and rearwards the main wheels.
U.S. Pat. No. 3,953,054 to Udden et al. discloses a hand operated wheel-chair with a pair of main wheels rigidly connected with the framework of the chair, at least one of which is either motor or hand operated and at least one castor wheel being pivotally connected with the framework of the chair and at least one support wheel being rigidly connected with the framework. At least one castor wheel and support wheel are positioned on each side of a line extending between the support points of the main wheels and at a level above the ground surface to permit either the castor or the support wheels to be in contact with the ground surface depending on whether the vertical through the center of gravity is located on one or the other side of the line between the support points of the main wheels. The wheel-chair also comprises a seat, which is disposed substantially mid-way between the main wheels and is supported by a transverse portion of the framework extending between the main wheels and being provided with a seat support in the form of a central column, which includes spring members for the seat and means for adjusting the height of the seat.
U.S. Pat. No. 4,245,847 to Knott discloses a wheelchair suitable for invalids or geriatric patients has a chair or seat supported on independent forward and rearward castor frames pivotally connected together at a transverse axis to form a castor frame assembly. The chair is pivotally mounted on the forward and rearward castor frames so that in negotiating a step or other obstacle, the lifting movement of the occupant is divided into stages so that a pleasant or comfortable ride is obtained. The wheelchair may be folded into a collapsed condition with the chair itself located between the castor frames.
U.S. Pat. No. 4,310,167 to McLaurin discloses a center of gravity wheelchair with an articulated chassis front and rear caster wheels, in which the main wheels and front and rear caster wheels are arranged in a diamond pattern, and the main wheels and rear caster wheel are carried by a subframe to form a bogie system, with the seat and front caster wheel carried by a seat frame assembly articulated with respect to the subframe through a pivoted link arrangement, whereby the seat may be moved forward relative to the main wheels, with a spring and damper connected between the subframe and seat frame assembly to minimize the tendency for the front caster wheel to lift off the ground when the main wheels are strongly propelled and to provide a shock absorbing structure for traversing rough ground. The diamond pattern provided by the wheels prevents lateral drift of the wheel chair when traversing sloping surfaces, and the articulated frame permits easier curb climbing.
U.S. Pat. No. 4,513,832 to Engman discloses a maneuverable, motor-driven wheeled chassis including a chassis structure carrying two pairs of support wheels separated in the longitudinal direction of the chassis. Between the pairs of support wheels there is a pair of drive wheels. The chassis structure includes a first frame structure carrying a first pair of support wheels and the pair of drive wheels, and a second frame structure carrying the second pair of support wheels and vertically pivotably connected to the first frame structure. The wheeled chassis is primarily intended for use as a wheelchair.
U.S. Pat. No. 4,538,857 to Engman discloses a foot rest arrangement for wheelchairs including a telescopic strut structure with an outer and an inner strut axially displaceable inside the outer strut, and a foot rest attached to the free lower end of one strut while the opposing free upper end of the other strut is attached to the wheelchair frame or to the forward portion of the chair seat frame, so that the strut structure carries the foot rest at a distance from the chair seat, this distance being variable by raising and lowering the foot rest and/or chair seat. Latching means are also arranged to lock the struts relative each other, with the foot rest at a given distance from the chair seat.
U.S. Pat. No. 5,183,133 to Roy et al. discloses a motorized wheel assembly provided in which there is a seat for receiving the occupant attached to a vertical shaft with a single central wheel mounted at the bottom of the shaft for rotation about a horizontal axis transverse to the chair and defining a direction of forward movement of the wheel forwardly of the chair. On the chair and the shaft is carried a battery and control unit for supplying power to the drive motor of the wheel mounted on the hub of the wheel. An outrigger frame includes a sleeve slideable on the shaft and a plurality of arms extending outwardly from the sleeve each arm carrying a castor wheel to prevent toppling of the device. Steering is achieved by the feet of the user applied to the outrigger frame to rotate the chair and the drivewheel about a vertical axis. The motor in a hub design of the wheel is achieved by providing a cylindrical housing surrounding the motor with annular bearings on the outer peripheral surface of the housing carrying the rim of the wheel which directly surrounds the housing. An output shaft at one end of the housing drives the rim through a coupling extending around the housing.
U.S. Pat. No. 5,435,404 to Garin, III discloses a power chair which is highly maneuverable and has a high degree of usable power. It provides maximum weight distribution to the pair of driving wheels of the vehicle unit. It greatly enhances the stability and provides an overall operating envelope of greatly reduced size, allowing the use of the vehicle in confined areas. The vehicle has a pair of drive wheels rotatably about a common axis which is transverse to the forward direction of the travel of the vehicle, the drive wheels being powered by respective drive motors. The center of mass of the vehicle and passenger is substantially in the vertical plane of the axis of the drive wheels. This arrangement increases the amount of weight for traction. The alignment of the mass with the axis of the driving wheels maximizes the resistance of the vehicle to steering deviations caused by centrifugal force. Stability fore and aft is provided by castering wheels placed in front of and behind the driving wheels. The rear wheel caster is preferably attached to a vertical pivoting swing arm. The movement of this arm is controlled by a spring and shock absorber assembly. However, the raw caster may be mounted with a rigid arm. Generally, at least one of the supporting arms must be spring biased to insure that substantially all wheels of vehicle remain on the ground, and also for shock absorbing purposes.
U.S. Pat. No. 5,445,233 to Fernie et al. discloses a multi-directional motorized wheelchair having a seat portion and, a back portion, and having two drive wheels, each having a separate motor for driving one drive wheel forwardly or backwardly, independently of the other wheel, a drive wheel mounting beneath the seat, and controls for operating the wheels either simultaneously in the same direction, or one of them in one direction, or simultaneously in opposite directions, and, stabilizer wheels mounted beneath the seat, and extending outwardly from and around the drive wheels, to stabilize the chair.
U.S. Pat. No. 5,592,997 to Ball discloses a wheelchair basically designed for mobility impaired children ages 2-6. The wheelchair is especially designed to facilitate the child""s access to all objects and activities that would normally be available to a non-disabled child. The chair includes a power base, including large front drive wheels and small rear casters, and a seat that is positioned directly over the drive wheels and that is readily detachable from the base. All components of the wheelchair arc positioned inboard of the side edges of the seat and inboard of the front edge of the seat so as to maximize, access to areas alongside of and in front of the wheelchair. The axis of rotation of the front drive wheels is generally vertically aligned with the trunk of the child positioned in the seat and the composite center of gravity of the child and wheelchair is positioned slightly behind the axis of rotation of the drive wheels so that the child can tilt the wheelchair forwardly about the axis of the front drive wheels by a simple forward rotation of the child""s trunk. The wheelchair also includes a stowable footrest that readily retracts into the base of the wheelchair.
U.S. Pat. No. 5,690,185 to Sengel discloses a self powered variable direction wheeled task chair, and a personal mobility device, providing additional ranges of motion in that it has an electrically powered height adjustable seat allowing the operator""s seating position to range from standard table height seating to work bench or counter top seating. Additionally and more importantly, the chair, will have directional movement capabilities well beyond typical wheel chairs, or other wheel driven personal mobility devices in that it will utilize electro-mechanical directionally pivoting propulsion, capable of not only forward, backward, and pivot turning capabilities, but also sideways movement or more precisely, movement in any direction, and a rotational movement as may be required by the operator.
U.S. Pat. No. 5,697,465 to Kruse discloses a personal mobility vehicle having a low center of gravity and compact overall size which facilitates travel in narrow hallways and in negotiating sharp turns both indoors and out of doors on smooth and uneven surfaces. The vehicle includes a generally horizontally disposed frame supported in close proximity above the ground by a pair of side-by-side space steerable rear wheels and two spaced motor-driven front wheels. A battery arrangement is connected to and supported by the frame and operably connected between a control lever in electrical communication with an electronic circuit and the motors for propelling the front wheels through a transaxle arrangement and for steering the rear wheel. By the side-by-side spaced fear wheel arrangement, steering angles of up to about 90 degrees are achieved without stalling propulsion. A seat is provided whereby a user""s feet may be comfortably supported on the frame or separate removable or fixed foot rests. Outrigger type anti-scuff and anti-tip wheels are also provided and may be in combination with a forwardly positioned ramp assist wheel connected beneath a forwardly perimeter of the frame to assist the vehicle in travelling over a ramp or bump.
U.S. Pat. No. 5,944,131 to Schaffner et al. discloses a front wheel drive power wheel chair having the drive wheel axis of rotation forward of the wheelchair user""s eyes and cranial center of perception.
Therefore it is an object of the present invention is to provide a central drive personal mobility vehicle which overcomes the aforementioned problems of the prior art and provide a significant advancement to the central drive personal mobility vehicle art.
Another object of the present invention is to provide a central drive personal mobility vehicle comprising an improved suspension system resulting in a superior stability for an operator.
Another object of the present invention is to provide a central drive personal mobility vehicle having an improved suspension system which reduces and/or substantially eliminates the jolting and abruptness encountered by operators of central drive personal mobility vehicles of the prior art.
Another object of the present invention is to provide a central drive personal mobility vehicle comprising an improved suspension system which substantially eliminates the pitch forward upon deceleration present in the central drive personal mobility vehicle of the prior art.
Another object of the present invention is to provide a central drive personal mobility vehicle comprising an improved suspension system which may be adjusted to accommodate for the weight distribution of the operator.
Another object of the present invention is to provide a central drive personal mobility vehicle comprising an improved suspension system which may be adjusted for either indoor operation on smooth surfaces or may be adjusted for outdoor operation on rough surfaces.
Another object of the present invention is to provide a central drive personal mobility vehicle having a superior ride and superior traction especially on inclined surfaces.
Another object of the present invention is to provide a central drive personal mobility vehicle having a pedestal for mounting a seat that is capable of accommodating a rotatable chair or a seat lift for assisting the operator in mounting and embarking from the central drive personal mobility vehicle.
Another object of the present invention is to provide a central drive personal mobility vehicle having a lightweight frame heretofore unknown in central drive personal mobility vehicles.
Another object of the present invention is to provide a central drive personal mobility vehicle which may be readily disassembled for transportation and shipping.
The foregoing has outlined some of the more pertinent objects of the present invention. These objects should be construed as being merely illustrative of some of the more prominent features and applications of the invention. Many other beneficial results can be obtained by applying the disclosed invention in a different manner or modifying the invention with in the scope of the invention. Accordingly other objects in a full understanding of the invention may be had by referring to the summary of the invention and the detailed description describing the preferred embodiment of the invention.
A specific embodiment of the present invention is shown in the attached drawings. For the purpose of summarizing the invention, the invention relates to an improved method and apparatus for a central drive personal mobility vehicle comprising a frame extending between a leading frame end and a trailing frame end thereby defining a leading frame portion, an intermediate frame portion and a trailing frame portion. The frame has a right and a left frame mounting located in the trailing frame portion of the frame. A seat is mounted to the intermediate portion of the frame.
The central drive personal mobility vehicle comprises a right and a left drive wheel assembly having a left and a right drive wheel. A right and a left leaf spring extends between a proximal end and a distal end. The proximal ends of the right and left leaf springs are secured to the right and left drive wheel assemblies, respectively. The distal ends of the right and left leaf springs are secured to the right and left frame mounting, respectively, for resiliently mounting the right and left drive wheel assemblies to the frame.
In a more specific embodiment of the invention, the leading frame portion and the trailing frame portion are adapted to receive a leading and a trailing battery. A pedestal extends substantially vertically upwardly from the intermediate frame portion of the frame with the seat being mounted to the pedestal.
In another embodiment of the invention, the right and left frame mounting include a right and a left socket for removably receiving the distal ends of the right and left leaf springs for removably securing the right and left drive wheel assemblies to the frame with the right and left drive wheels positioned substantially below the seat. Preferably, the right and left springs are adjustable for adjusting the effective stiffness of the right and left springs.
In another embodiment of the invention, the right and left drive wheel assembly comprise a right and a left gear box with a right and a left motor connected to the right and left gear box for driving the right and left drive wheels. The right and left leaf springs are secured to the right and left gear boxes and extend toward the trailing frame end of the frame. A linking bar interconnects the first and second gear boxes.
A right and a left leading wheel are rigidly secured to the right and left drive wheel assemblies and are located in proximity to the leading frame end of the frame. The right and left leaf springs simultaneously resiliently secure the right and left drive wheels and the right and left leading wheels relative to the frame.
A trailing wheel support is pivotably mounted to the intermediate frame portion of the frame. A right and a left trailing wheel are rotatably mounted to the trailing wheel support and are located in proximity to the trailing frame end of the frame.
The foregoing has outlined rather broadly the more pertinent and important features of the present invention in order that the detailed description that follows may be better understood so that the present contribution to the art can be more fully appreciated. Additional features of the invention will be described hereinafter which form the subject matter of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention.